1. Field of The Invention
This invention relates to bonders which are employed to make electrical connection between electrodes or pads on semi-conductor devices and lead-out pads. More specifically, the present invention relates to apparatus and processes for detecting whether the interconnect material used during the bonding processing is missing.
2. Description of Related Art
Machines which make electrical connections between electrodes or pads on semi-conductor devices and lead-out pads are well-known. Two such machines are illustrated in U.S. Pat. Nos. 4,817,848 and 4,718,591.
Sometimes during the use of these machines, the interconnect material is not present at the interconnect site when it should be. Unless its absence is quickly detected, tool damage can result, together with damage to successive interconnect sites. The need to promptly detect the absence of interconnect material from the bonding site, therefore, has existed, as illustrated by the missing wire detector disclosed in U.S. Pat. No. 4,558,596.
The techniques used in the past to detect missing interconnect material, such as ultrasonics impedance measurement, has suffered from certain problems. These problems include great sensitivity to set up parameters, to bonding tool types, and to spurious loading errors introduced by material irregularities at the target surface or in the interconnect material. Other problems are also present.